First: You clearly have no idea what Calvinism teaches, so sell your strawdummy elsewhere.
So then give us an answer, oh great one:
Does Calvinism teach unconditional eternal security or does it teach conditional eternal security?
The claim is silly anyhow, that God being righteous could not permit a large amount of evildoing in the world with God’s full knowledge.
Given that Deal A for the world has been blown and it would have gone to hell if there was nothing else, anything better than that is... better.